Don't clobber a Python exception with an unknown error

Close #410

2 files changed, 5 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 84be201..a0399a1 100644
--- a/NEWS
+++ b/NEWS
@@ -7,6 +7,7 @@ What's new in psycopg 2.7.2
 - Fixed inconsistent state in externally closed connections
   (:tickets:`#263, #311, #443`). Was fixed in 2.6.2 but not included in
   2.7 by mistake.
+- Fixed Python exceptions propagation in green callback (:ticket:`#410`).
 - Don't display the password in `connection.dsn` when the connection
   string is specified as an URI (:ticket:`#528`).
 - Return objects with timezone parsing "infinity" :sql:`timestamptz`
diff --git a/psycopg/pqpath.c b/psycopg/pqpath.c
index f270ce8..5572072 100644
--- a/psycopg/pqpath.c
+++ b/psycopg/pqpath.c
@@ -451,6 +451,10 @@ pq_complete_error(connectionObject *conn, PGresult **pgres, char **error)
     else {
         if (*error != NULL) {
             PyErr_SetString(OperationalError, *error);
+        } else if (PyErr_Occurred()) {
+            /* There was a Python error (e.g. in the callback). Don't clobber
+             * it with an unknown exception. (see #410) */
+            Dprintf("pq_complete_error: forwarding Python exception");
         } else {
             PyErr_SetString(OperationalError, "unknown error");
         }